Encipher-decipher device having semi-automatic generation of the code key during data entry

Abstract

An encipher-decipher apparatus including an input keyboard and a processing and control stage which enciphers or deciphers data received directly from the keyboard or preferably from a text store with the aid of a cipher generator. The cipher generator produces a cipher sequence dependent on two code data items that determine the initial state of the cipher generator. One item for encryption is supplied as a set of random code characters from a random generator. The random generator comprises a continually cycled modulo-n counter and a FIFO memory into which the instantaneous state of the counter is entered at each of successive actuations of keys of the keyboard, such key operations being those done in any event in the use of the apparatus. The cycle time of the counter is much less than the time between consecutive key operations. A clock rate of 100 kHz is suggested. The set of characters is read out of the FIFO store at the start of data processing for use by the cipher generator.

What is claimed is: 
     
       1. Apparatus for data encryption comprising an input keyboard, an encipher-decipher stage for processing data which includes a cipher generator that produces a cipher pulse sequence dependent on a code item supplied thereto in the form of a set of code characters, and a random code generator coupled to said cipher generator for generating said code item, the improvement wherein: said random code generator comprises means for generating code characters and a store coupled thereto for holding a set of code characters; and   said keyboard having an output coupled to the random code generator to control same and cause a random code character to be entered in the store on each actuation of any random key in at least a group of the keys of the keyboard.   
     
     
       2. Apparatus for data encryption as claimed in claim 1 in which said code character generating means comprises a continually cycling modulo-n counter coupled to said store, and said keyboard control causing the instantaneous state of the counter to be entered into the store at each of said key actuations. 
     
     
       3. Apparatus for data encryption as claimed in claim 1 comprising function control means for reading the set of random code characters out of said store to said cipher generator. 
     
     
       4. Apparatus for data encryption as claimed in claim 2 comprising function control means for reading the set of random code characters out of said store to said cipher generator. 
     
     
       5. Apparatus for data encryption as claimed in claim 3 in which said code character generating means is continually operative to produce a repeated sequence of code characters and said keyboard output is operable to control the moment of entry of a code character into said store at each of said keyboard actuations. 
     
     
       6. Apparatus for data encryption as claimed in claim 5 in which the period for generating one code character sequence is much less than the shortest possible time between two consecutive operations of the keyboard. 
     
     
       7. Apparatus for data encryption as claimed in claim 2 in which said counter is clocked at frequency in the range of 1 to 500 kHz. 
     
     
       8. Apparatus as claimed in claim 2 in which the counter performs not less than one complete cycle in the shortest possible time between two consecutive operations of the keyboard. 
     
     
       9. Apparatus for data encryption as claimed in claim 8 in which in said shortest possible time, the counter performs a plurality of cycles in the range of 10 to 100 cycles. 
     
     
       10. Apparatus for data encryption as claimed in claim 2 in which said store comprises a FIFO store. 
     
     
       11. Apparatus for data encryption-decryption comprising an input keyboard, an encipher-decipher stage for processing data, including a cipher generator operable to produce a cipher pulse sequence dependent on its initial state at the start of data processing data, said initial state being determined by two code data items, a random code generator for producing one of said code data items, and means for controlling the sequence of functions within the apparatus, wherein: said random code generator comprising means for generating code characters and a store coupled thereto for holding a set of such code characters to constitute said one code data item, and said random code generator being coupled to said keyboard to be controlled by the actuation of any random key of at least a group of keys of the keyboard such that the selection of successive code characters for entry in the store is timed by successive key actuations.   
     
     
       12. Apparatus for data encryption-decryption as claimed in claim 11 in which said code character generating means is operable to generate a repeated sequence of code characters and each of said key actuations causes the instantaneous code character to be entered into said store. 
     
     
       13. Apparatus for data encryption-decryption as claimed in claim 12 in which the time of one sequence of code characters is much less than the minimum time between two consecutive operations of the keyboard. 
     
     
       14. Apparatus for data encryption-decryption as claimed in claim 12 in which said store comprises a FIFO store having an input for receiving a signal to cause the read-in of a code character to the store, said FIFO input being coupled to said keyboard to receive a read-in signal in response to each of said key actuations, and said FIFO store having an input for receiving a signal from said functions sequence control means to read-out the set of code characters in said FIFO store.